taglib: warn the user when the embedded image is invalid (i.e. was embedded by a broken version of iTunes)

taglib: Supports in ogg/vorbis base64 encoded embedded album art with COVERARTMIME & COVERART comments.
    Use TagLib namespace for better code readability.

demuxers: Adds attachments support for ogg.
    Fix potential memleaks.

notify: unref the notification popup after we have finished using it. fix a big memory leak, and potential crashes.

  Someone should check if we could make xtag not send ENDELEM for self-closing tags, as libxml doesn't.

(libmpeg2/xvmc pending)

 - Remove configurable boundary that had never been working anyway (did not match the original value from MUX_GET_MIME)

the only demuxer supported is mpga, other demuxers should be updated if they demux files that can have id3v2 tags
fix some bugs in flac & ogg demuxers

The idle HTTP interace is down from 30 to 10 wakeups/s (I think the remaining ones are due to HTTPd core).

 - Really yield the input (and release it) on a need-basis in the HTTP handler rather than in a custom thread. This is probably not thread-safe, but it's less unsafe than the previous code anyway.
This makes the HTTP interface thread very much useless, niark niark

LibVLC always creates the (singleton) playlist before the interfaces anyway.
Besides, the HTTP interface callbacks assumes the playlist is yield.
This removes one of two reasons for running the damn HTTP interface thread.